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<p><code><strong>Math.abs(x)</strong></code> 函数返回指定数字 “x“ 的绝对值。如下：</p>
<p><math display="block"><semantics><mrow><mstyle mathvariant="monospace"><mrow><mo lspace="0em" rspace="thinmathspace">Math.abs</mo><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></mstyle><mo>=</mo><mrow><mo stretchy="false">|</mo><mi>x</mi><mo stretchy="false">|</mo></mrow><mo>=</mo><mrow><mo>{</mo><mtable columnalign="left left"><mtr><mtd><mi>x</mi></mtd><mtd><mtext>if</mtext><mspace width="1em"></mspace><mi>x</mi><mo>≥</mo><mn>0</mn></mtd></mtr><mtr><mtd><mo>-</mo><mi>x</mi></mtd><mtd><mtext>if</mtext><mspace width="1em"></mspace><mi>x</mi><mo>&lt;</mo><mn>0</mn></mtd></mtr></mtable></mrow></mrow><annotation encoding="TeX">{\mathtt{\operatorname{Math.abs}(x)}} = {|x|} = \begin{cases} x &amp; \text{if} \quad x \geq 0 \\ -x &amp; \text{if} \quad x &lt; 0 \end{cases} </annotation></semantics></math></p>
<h2 id="Syntax" name="Syntax">语法</h2>
<pre><code class="language-javascript">Math.abs(<em>x</em>);</code></pre>
<h3 id="Parameters" name="Parameters">参数</h3>
<dl>
<dt><code>x</code></dt>
<dd>一个数值</dd>
</dl>
<h2 id="Description" name="Description">说明</h2>
<p><code><font face="Open Sans, sans-serif"><span style="line-height: 21px;">由于 </span></font>Math.abs()</code> <code>是</code> <code>Math</code> 中的一个静态方法，你应该通过 <code>Math.abs()</code> <code>调用。</code>（Math 不是构造器）</p>
<h2 id="Examples" name="Examples">示例</h2>
<h3 id="Example:_Math.abs_behavior" name="Example:_Math.abs_behavior"><code>Math.abs()函数的行为</code></h3>
<p>传入一个非数字形式的字符串或者 undefined/empty 变量，将返回 <code>NaN</code>。传入 null 将返回 0。</p>
<pre><code class="language-js">Math.abs('-1');     // 1
Math.abs(-2);       // 2
Math.abs(null);     // 0
Math.abs("string"); // NaN
Math.abs();         // NaN</code></pre>
<h2 id="规范">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">规范版本</th>
<th scope="col">规范状态</th>
<th scope="col">注解</th>
</tr>
<tr>
<td>ECMAScript 1st Edition. Implemented in JavaScript 1.0</td>
<td>Standard</td>
<td>Initial definition.</td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/5.1/#sec-15.8.2.1" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">Math.abs</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-math.abs" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Math.abs</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p></p><div class="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
            This compatibility table still uses the old format,
            because we haven't yet converted the data it contains.
            <strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
<div class="htab">
<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
<ul>
<li class="selected"><a>Desktop</a></li>
<li><a>Mobile</a></li>
</ul>
</div><p></p>
<div id="compat-desktop">
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Chrome</th>
<th>Firefox (Gecko)</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari</th>
</tr>
<tr>
<td>Basic support</td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
</tr>
</tbody>
</table>
</div>
<div id="compat-mobile">
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Android</th>
<th>Chrome for Android</th>
<th>Firefox Mobile (Gecko)</th>
<th>IE Mobile</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
</tr>
<tr>
<td>Basic support</td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
</tr>
</tbody>
</table>
</div>
<h2 id="See_also" name="See_also">相关链接</h2>
<ul>
<li>The <a href="Reference/Global_Objects/Math" title="Math 是一个内置对象， 它具有数学常数和函数的属性和方法。不是一个函数对象。"><code>Math</code></a> object it belongs to.</li>
<li><a href="Reference/Global_Objects/Math/ceil" title="Math.ceil() 函数返回大于或等于一个给定数字的最小整数。"><code>Math.ceil()</code></a></li>
<li><a href="Reference/Global_Objects/Math/floor" title="Math.floor() 返回小于或等于一个给定数字的最大整数。"><code>Math.floor()</code></a></li>
<li><a href="Reference/Global_Objects/Math/round" title="Math.round() 函数返回一个数字四舍五入后最接近的整数。"><code>Math.round()</code></a></li>
</ul>
</article>